Direct-sequence spread-spectrum communication systems incorporate a modulation technique in which a narrow-band signal is spread over a broad frequency range using a spreading function known to both the transmitter and the receiver. While such a signal may contain a significant amount of total energy, the energy at any given frequency is minimal, even below the level of background noise. This allows the signal to blend into the noise.
Since the energy contained in the signal is very low at any given frequency, the signal is susceptible to interference, either coincidental or intentional. Narrow-band interference may insert sufficient energy to become spread over a broad frequency range during receiver processing and mask portions of the signal at the requisite specific frequencies. When such a signal is detected using conventional spread-spectrum reception techniques, the interference may produce false correlations and/or mask true correlations. Hence, the intelligence within the signal may be altered or obscured.